Navigating a UAV with on-board navigation algorithms with flight depiction

ABSTRACT

Navigating a UAV including receiving in a remote control device a user&#39;s selection of a GUI map pixel that represents a waypoint for UAV navigation, mapping the pixel&#39;s location on the GUI to Earth coordinates of the waypoint, transmitting the coordinates of the waypoint to the UAV, reading a starting position from a GPS receiver on the UAV, and piloting the UAV, under control of a navigation computer on the UAV, from the starting position to the waypoint in accordance with a navigation algorithm. While piloting the UAV from the starting position to the waypoint, such embodiments include reading from the GPS receiver a sequence of GPS data representing a flight path of the UAV, and depicting the flight of the UAV with 3D computer graphics, including a computer graphic display of a satellite image of the Earth, in dependence upon the GPS data.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention is data processing, or, more specifically,methods, systems, and products for navigating an unmanned aerial vehicle(“UAV”).

2. Description of Related Art

Many forms of UAV are available in prior art, both domestically andinternationally. Their payload weight carrying capability, theiraccommodations (volume, environment), their mission profiles (altitude,range, duration), and their command, control and data acquisitioncapabilities vary significantly. Routine civil access to these variousUAV assets is in an embryonic state.

Conventional UAVs are typically manually controlled by an operator whomay view aspects of a UAV's flight using cameras installed on the UAVwith images provided through downlink telemetry. Navigating such UAVsfrom a starting position to one or more waypoints requires an operatorto have specific knowledge of the UAV's flight, including such aspectsas starting location, the UAV's current location, waypoint locations,and so on. Operators of prior art UAVs usually are required generally tomanually control the UAV from a starting position to a waypoint withlittle aid from automation. There is therefore an ongoing need forimprovement in the area of UAV navigations.

SUMMARY OF THE INVENTION

Methods, systems, and products are described for UAV navigation thatenable an operator to input a single interface operation, a mouseclickor joystick button click, thereby selecting GUI pixel from a displayedmap of the surface of the Earth. The selected pixel maps to a waypoint.The waypoint is uploaded through uplink telemetry to a UAV whichcalculates a heading and flies, according to a navigation algorithm, acourse to the waypoint. The heading is not necessarily the course ifwind is present, depending on the navigation algorithm chosen for theflight. All this occurs with a single keystroke or mouseclick from theoperator.

The operator's remote control device from which the pixel is selected isenabled according to embodiments of the present invention to be verythin. Often the remote control device can be a browser in a laptop orpersonal computer or a microbrowser in a PDA enhanced only withclient-side scripting sufficient to map a pixel to a waypoint andtransmit the waypoint to the UAV. The UAV itself generally comprises theintelligence, the navigation algorithms, a web server to download mapimages to a client browser in a remote control device, a repository ofLandsat maps from which HTML screens are formulated for download to theremote control device, and so on.

In addition to uplinking a single waypoint, operators of remote controldevices according to embodiments of the present invention are enabled toenter through a user interface and upload to the UAV many waypointswhich taken in sequence form an entire mission for a UAV that flies fromwaypoint to waypoint, eventually returning to a starting point. Inaddition to providing for a mission route comprising many waypoints,typical embodiments also support ‘macros,’ sets of UAV instructionsassociated with waypoints. Such UAV instructions can include, forexample, instructions to orbit, take photographs or stream video, andcontinue flying a route or mission to a next waypoint. Because waypointsare entered with selected pixels and macros may be created by selectingUAV instructions from a pull down menu in a GUI, complex missions may beestablished with a few keystrokes of mouseclicks on an interface of aremote control device. Because the waypoints and UAV instructions areuploaded and stored on the UAV along with the navigation algorithmsneeded to travel from waypoint to waypoint, the remote control devicemay lose communications with the UAV or even be destroyed completely,and the UAV will simply continue its mission.

More particularly, methods, systems, and products are disclosed in thisspecification for navigating a UAV. Typical embodiments includereceiving in a remote control device a user's selection of a GUI mappixel that represents a waypoint for UAV navigation, the pixel having alocation on the GUI, mapping the pixel's location on the GUI to Earthcoordinates of the waypoint, transmitting the coordinates of thewaypoint to the UAV, reading a starting position from a GPS receiver onthe UAV, and piloting the UAV, under control of a navigation computer onthe UAV, from the starting position to the waypoint in accordance with anavigation algorithm. While piloting the UAV from the starting positionto the waypoint, such embodiments include reading from the GPS receivera sequence of GPS data representing a flight path of the UAV, anddepicting the flight of the UAV with 3D computer graphics, including acomputer graphic display of a satellite image of the Earth, independence upon the GPS data.

In many embodiments, depicting the flight of the UAV includesdetermining, on the UAV, a display attitude of the UAV in dependenceupon the sequence of GPS data, calculating, on the UAV, from thesequence of GPS data, the UAV's course, creating, on the UAV, images fordisplay in dependence upon the display attitude, the course, and asatellite image stored on the UAV, and downloading the images fordisplay from the UAV to the remote control device. In some embodiments,depicting the flight of the UAV includes downloading the GPS sequencefrom the UAV to the remote control device, determining, in the remotecontrol device, a display attitude of the UAV in dependence upon thesequence of GPS data, calculating, in the remote control device, fromthe sequence of GPS data, the UAV's course, and creating, in the remotecontrol device, images for display in dependence upon the displayattitude, the course, and a satellite image stored on the remote controldevice.

In many embodiments, depicting the flight of the UAV includesdetermining a display attitude of the UAV in dependence upon thesequence of GPS data, including detecting changes in the UAV's coursefrom the sequence of GPS data, and determining a display roll angle independence upon the detected course changes. In some embodiments,depicting the flight of the UAV includes determining a display attitudeof the UAV in dependence upon the sequence of GPS data, includingdetecting changes in the UAV's course from the sequence of GPS data, anddetermining a display yaw angle in dependence upon the detected coursechanges. In many embodiments, depicting the flight of the UAV includesdetermining a display attitude of the UAV in dependence upon thesequence of GPS data, including detecting changes in the UAV's altitudefrom the sequence of GPS data, determining a display pitch angle independence upon the detected altitude changes.

Many embodiments include receiving user selections of a multiplicity ofGUI map pixels representing waypoints, each pixel having a location onthe GUI, mapping each pixel location to Earth coordinates of a waypoint,assigning one or more UAV instructions to each waypoint, transmittingthe coordinates of the waypoints and the UAV instructions to the UAV,storing the coordinates of the waypoints and the UAV instructions incomputer memory on the UAV, piloting the UAV to each waypoint inaccordance with one or more navigation algorithms, and operating the UAVat each waypoint in accordance with the UAV instructions for eachwaypoint. In some embodiments, mapping the pixel's location on the GUIto Earth coordinates of the waypoint includes mapping pixel boundariesof the GUI map to Earth coordinates, identifying a range of latitude anda range of longitude represented by each pixel, and locating a region onthe surface of the Earth in dependence upon the boundaries, the ranges,and the location of the pixel on the GUI map.

In many embodiments, wherein locating a region on the surface of theEarth in dependence upon the boundaries, the ranges, and the location ofthe pixel on the GUI map includes multiplying the range of longituderepresented by each pixel by a column number of the selected pixel,yielding a first multiplicand, multiplying the range of longituderepresented by each pixel by 0.5, yielding a second multiplicand, addingthe first and second multiplicands to an origin longitude of the GUImap, multiplying the range of latitude represented by each pixel by arow number of the selected pixel, yielding a third multiplicand,multiplying the range of latitude represented by each pixel by 0.5,yielding a fourth multiplicand, and adding the third and fourthmultiplicands to an origin latitude of the GUI map.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescriptions of exemplary embodiments of the invention as illustrated inthe accompanying drawings wherein like reference numbers generallyrepresent like parts of exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 sets forth a system diagram illustrating relations amongcomponents of an exemplary system for navigating a UAV.

FIG. 2 is a block diagram of an exemplary UAV showing relations amongcomponents of included automated computing machinery.

FIG. 3 is a block diagram of an exemplary remote control device showingrelations among components of included automated computing machinery.

FIG. 4 sets forth a flow chart illustrating an exemplary method fornavigating a UAV that includes receiving in a remote control device auser's selection of a GUI map pixel that represents a waypoint for UAVnavigation.

FIG. 4A sets forth a flow chart illustrating an exemplary method ofdepicting the flight of the UAV.

FIG. 4B sets forth a flow chart illustrating another exemplary method ofdepicting the flight of the UAV.

FIG. 5 sets forth a block diagram that includes a GUI displaying a mapand a corresponding area of the surface of the Earth.

FIG. 6 sets forth a flow chart illustrating an exemplary method ofpiloting in accordance with a navigation algorithm.

FIG. 7 sets forth a line drawing illustrating a flight path produced byapplication of the method of FIG. 6.

FIG. 8 sets forth a flow chart illustrating an exemplary method ofpiloting in accordance with a navigation algorithm.

FIG. 9 sets forth a line drawing illustrating a flight path produced byapplication of the method of FIG. 8.

FIG. 10 sets forth a flow chart illustrating an exemplary method ofpiloting in accordance with a navigation algorithm.

FIG. 11 sets forth a line drawing illustrating a flight path produced byapplication of the method of FIG. 10.

FIG. 12 sets forth a flow chart illustrating an exemplary method ofpiloting in accordance with a navigation algorithm.

FIG. 12A sets forth a line drawing illustrating a method of calculatinga heading with a cross wind to achieve a particular ground course.

FIG. 13 sets forth a line drawing illustrating a flight path produced byapplication of the method of FIG. 12.

FIG. 14 sets forth a flow chart illustrating an exemplary method ofpiloting in accordance with a navigation algorithm.

FIG. 15 sets forth a line drawing illustrating a flight path produced byapplication of the method of FIG. 14.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Introduction

The present invention is described to a large extent in thisspecification in terms of methods for navigating a UAV. Persons skilledin the art, however, will recognize that any computer system thatincludes suitable programming means for operating in accordance with thedisclosed methods also falls well within the scope of the presentinvention. Suitable programming means include any means for directing acomputer system to execute the steps of the method of the invention,including for example, systems comprised of processing units andarithmetic-logic circuits coupled to computer memory, which systems havethe capability of storing in computer memory, which computer memoryincludes electronic circuits configured to store data and programinstructions, programmed steps of the method of the invention forexecution by a processing unit.

The invention also may be embodied in a computer program product, suchas a diskette or other recording medium, for use with any suitable dataprocessing system. Embodiments of a computer program product may beimplemented by use of any recording medium for machine-readableinformation, including magnetic media, optical media, or other suitablemedia. Persons skilled in the art will immediately recognize that anycomputer system having suitable programming means will be capable ofexecuting the steps of the method of the invention as embodied in aprogram product. Persons skilled in the art will recognize immediatelythat, although most of the exemplary embodiments described in thisspecification are oriented to software installed and executing oncomputer hardware, nevertheless, alternative embodiments implemented asfirmware or as hardware are well within the scope of the presentinvention.

Definitions

“Air speed” means UAV air speed, the speed of the UAV through the air.

A “cross track” is a fixed course from a starting point directly to awaypoint. A cross track has a direction, a ‘cross track direction,’ thatis the direction straight from a starting point to a waypoint. That is,a cross track direction is the heading that a UAV would fly directlyfrom a starting point to a waypoint in the absence of wind.

“GUI” means graphical user interface, a display means for a computerscreen.

“Heading” means the compass heading of the UAV. “Course” means thedirection of travel of the UAV over the ground. That is, a “course” inthis specification is what is called, in some lexicons of airnavigation, a ‘track.’ In the absence of wind, or in the presence of astraight tailwind or straight headwind, the course and the heading arethe same direction. In the presence of crosswind, the course and theheading are different directions.

“Position” refers to a location in the air or over the ground.‘Position’ is typically specified as Earth coordinates, latitude andlongitude. A specification of position may also include altitude.

A “waypoint” is a position chosen as a destination for navigation of aroute. A route has one or more waypoints. That is, a route is composedof waypoints, including at least one final waypoint, and one or moreintermediate waypoints.

“TDMA” stands for Time Division Multiple Access, a technology fordelivering digital wireless service using time-division multiplexing.TDMA works by dividing a radio frequency into time slots and thenallocating slots to multiple calls. In this way, a single frequency cansupport multiple, simultaneous data channels. TDMA is used by GSM.

“GSM” stands for Global System for Mobile Communications, a digitalcellular standard. GSM at this time is the de facto standard forwireless digital communications in Europe and Asia.

“CDPD” stands for Cellular Digital Packet Data, a data transmissiontechnology developed for use on cellular phone frequencies. CDPD usesunused cellular channels to transmit data in packets. CDPD supports datatransfer rates of up to 19.2 Kbps.

“GPRS” stands for General Packet Radio Service, a standard for wirelessdata communications which runs at speeds up to 150 Kbps, compared withcurrent GSM systems which cannot support more than about 9.6 Kbps. GPRS,which supports a wide range of speeds, is an efficient use of limitedbandwidth and is particularly suited for sending and receiving smallbursts of data, such as e-mail and Web browsing, as well as largevolumes of data.

“EDGE” stands for Enhanced Data Rates for GSM Evolution, a standard forwireless data communications supporting data transfer rates of more than300 Kbps. GPRS and EDGE are considered interim steps on the road toUMTS.

“UMTS” stands for Universal Mobile Telecommunication System, a standardfor wireless data communications supporting data transfer rates of up to2 Mpbs. UMTS is also referred to W-CDMA for Wideband Code DivisionMultiple Access.

Navigating a UAV with On-board Navigation Algorithms With FlightDepiction

Methods, systems, and products for navigating a UAV are explained withreference to the accompanying drawings, beginning with FIG. 1. FIG. 1sets forth a system diagram illustrating relations among components ofan exemplary system for navigating a UAV. The system of FIG. 1 includesUAV (100) which includes a GPS (Global Positioning System) receiver (notshown) that receives a steady stream of GPS data from satellites (190,192). For convenience of explanation, only two GPS satellites are shownin FIG. 1, although the GPS satellite network in fact includes 24 GPSsatellites.

The system of FIG. 1 operates to navigate a UAV by receiving in a remotecontrol device a user's selection of a GUI map pixel that represents awaypoint for UAV navigation. Each such pixel has a location on a GUImap, typically specified as a row and column position. Examples ofremote control devices in FIG. 1 include mobile telephone (110),workstation (104), laptop computer (116), and PDA (Personal DigitalAssistant) (120). Each such remote control device is capable ofsupporting a GUI display of a map of the surface of the Earth in whicheach pixel on the GUI map represents a position on the Earth.

Each remote control device also supports at least one user input devicethrough which a user may enter the user's selection of a pixel. Examplesof user input devices in the system of FIG. 1 include telephone keypad(122), workstation keyboard (114), workstation joystick (112), laptopkeyboard (116) and PDA touch screen (118).

The system of FIG. 1 typically is capable of operating a remote controldevice to map the pixel' location on the GUI to Earth coordinates of awaypoint and to transmit the coordinates of the waypoint to the UAV(100). In the example of FIG. 1, waypoint coordinates are generallytransmitted from remote control devices to the UAV through wirelessnetwork (102). Wireless network (102) is implemented using any wirelessdata transmission technology as will occur to those of skill in the artincluding, for example, TDMA, GSM, CDPD, GPRS, EDGE, and UMTS. In apreferred embodiment, a data communications link layer is implementedusing one of these technologies, a data communications network layer isimplemented with the Internet Protocol (“IP”), and a data communicationstransmission layer is implemented using the Transmission ControlProtocol (“TCP”). In such systems, telemetry between the UAV and remotecontrol devices, including waypoint coordinates, are transmitted usingan application-level protocol such as, for example, the HyperTextTransmission Protocol (“HTTP”), the Wireless Application Protocol(“WAP”), the Handheld Device Transmission Protocol (“HDTP”), or anyother data communications protocol as will occur to those of skill inthe art.

The system of FIG. 1 typically is capable of operating a UAV to read astarting position from a GPS receiver (reference 186 on FIG. 2) on theUAV and pilot the UAV, under control of a navigation computer on theUAV, from a starting position to a waypoint in accordance with anavigation algorithm. The system of FIG. 1 is also capable of readingfrom the GPS receiver on the UAV a sequence of GPS data representing aflight path of the UAV and depicting the flight of the UAV with 3Dcomputer graphics while the UAV is piloting under control of anavigation computer on the UAV.

UAVs according to embodiments of the present invention typicallyinclude, not only an aircraft, but also automated computing machinerycapable of receiving GPS data, operating telemetry between the UAV andone or more remote control devices, and navigating a UAV amongwaypoints. FIG. 2 is a block diagram of an exemplary UAV showingrelations among components of included automated computing machinery. InFIG. 2, UAV (100) includes a processor (164), also typically referred toas a central processing unit or ‘CPU.’ The processor may be amicroprocessor, a programmable control unit, or any other form ofprocessor useful according to the form factor of a particular UAV aswill occur to those of skill in the art. Other components of UAV (100)are coupled for data transfer to processor (164) through system bus(100).

UAV (100) includes random access memory or ‘RAM’ (166). Stored in RAM(166) is an application program (158) that implements inventive methodsaccording to embodiments of the present invention. In some embodiments,the application programming runs on an OSGi services framework (156).OSGi Stands for ‘Open Services Gateway Initiative.’ The OSGispecification is a Java-based application layer framework that providesvendor neutral application layer APIs and functions. An OSGi serviceframework (126) is written in Java and therefore typically runs on aJava Virtual Machine (JVM) (154) which in turn runs on an operatingsystem (150). Examples of operating systems useful in UAVs according tothe present invention include Unix, AIX™, and Microsoft Windows™.

In OSGi, the framework is a hosting platform for running ‘services’.Services are the main building blocks for creating applicationsaccording to the OSGi. A service is a group of Java classes andinterfaces that implement a certain feature. The OSGi specificationprovides a number of standard services. For example, OSGi provides astandard HTTP service that can respond to requests from HTTP clients,such as, for example, remote control devices according to embodiments ofthe present invention. That is, such remote control devices are enabledto communicate with a UAV having an HTTP service by use of datacommunications messages in the HTTP protocol.

Services in OSGi are packaged in ‘bundles’ with other files, images, andresources that the services need for execution. A bundle is a Javaarchive or ‘JAR’ file including one or more service implementations, anactivator class, and a manifest file. An activator class is a Java classthat the service framework uses to start and stop a bundle. A manifestfile is a standard text file that describes the contents of the bundle.

The services framework in OSGi also includes a service registry. Theservice registry includes a service registration including the service'sname and an instance of a class that implements the service for eachbundle installed on the framework and registered with the serviceregistry. A bundle may request services that are not included in thebundle, but are registered on the framework service registry. To find aservice, a bundle performs a query on the framework's service registry.

In the UAV (100) of FIG. 2, software programs and other usefulinformation may be stored in RAM or in non-volatile memory (168).Non-volatile memory (168) may be implemented as a magnetic disk drivesuch as a micro-drive, an optical disk drive, static read only memory(‘ROM’), electrically erasable programmable read-only memory space(‘EEPROM’ or ‘flash’ memory), or otherwise as will occur to those ofskill in the art. UAV (100) includes communications adapter (170)implementing data communications connections (184) to other computers(162), which may be wireless networks, satellites, remote controldevices, servers, or others as will occur to those of skill in the art.Communications adapters implement the hardware level of datacommunications connections through which UAVs transmit wireless datacommunications. Examples of communications adapters include wirelessmodems for dial-up connections through wireless telephone networks.

UAV (100) includes servos (178). Servos (178) are proportional controlservos that convert digital control signals from system bus (160) intoactual proportional displacement of flight control surfaces, ailerons,elevators, and the rudder. The displacement of flight control surfacesis ‘proportional’ to values of digital control signals, as opposed tothe ‘all or nothing’ motion produces by some servos. In this way,ailerons, for example, may be set to thirty degrees, sixty degrees, orany other supported angle rather than always being only neutral or fullyrotated. Several proportional control servos useful in various UAVsaccording to embodiments of the present invention are available fromFutaba®.

UAV (100) includes a servo control adapter (172). A servo controladapter (172) is multi-function input/output servo motion controllercapable of controlling several servos. An example of such a servocontrol adapter is the “IOSERVO” model from National Control Devices ofOsceola, Mo. The IOSERVO is described on National Control Deviceswebsite at www.controlanything.com.

UAV (100) includes a flight stabilizer system (174). A flight stabilizersystem is a control module that operates servos (178) to automaticallyreturn a UAV to straight and level flight, thereby simplifying the workthat must be done by navigation algorithms. An example of a flightstabilizer system useful in various embodiments of UAVs according to thepresent invention is model Co-Pilot_(™)from FMA, Inc., of Frederick, Md.The Co-Pilot flight stabilizer system identifies a horizon with heatsensors, identifies changes in aircraft attitude relative to thehorizon, and sends corrective signals to the servos (178) to keep theUAV flying straight and level.

UAV (100) includes an AVCS gyro (176). An AVCS gryo is an angular vectorcontrol system gyroscope that provides control signal to the servos tocounter undesired changes in attitude such as those caused by suddengusts of wind. An example of an AVCS gyro useful in various UAVsaccording to the present invention is model GYA350 from Futaba®.

Remote control devices according to embodiments of the present inventiontypically comprise automated computing machinery capable of receivinguser selections of pixel on GUI maps, mapping the pixel to a waypointlocation, and transmitting the waypoint location to a UAV. FIG. 3 is ablock diagram of an exemplary remote control device showing relationsamong components of included automated computing machinery. In FIG. 3,remote control device (161) includes a processor (164), also typicallyreferred to as a central processing unit or ‘CPU.’ The processor may bea microprocessor, a programmable control unit, or any other form ofprocessor useful according to the form factor of a particular remotecontrol device as will occur to those of skill in the art. Othercomponents of remote control device (161) are coupled for data transferto processor (164) through system bus (160).

Remote control device (161) includes random access memory or ‘RAM’(166). Stored in RAM (166) an application program 152 that implementsinventive methods of the present invention. In some embodiments, theapplication program (152) is OSGi compliant an therefore runs on an OSGiservices framework installed (not shown) on a JVM (not shown). Inaddition, software programs and further information for use inimplementing methods of navigating a UAV according to embodiments of thepresent invention may be stored in RAM or in non-volatile memory (168).Non-volatile memory (168) may be implemented as a magnetic disk drivesuch as a micro-drive, an optical disk drive, static read only memory(‘ROM’), electrically erasable programmable read-only memory space(‘EEPROM’ or ‘flash’ memory), or otherwise as will occur to those ofskill in the art.

Remote control device (161) includes communications adapter (170)implementing data communications connections (184) to other computers(162), including particularly computes on UAVs. Communications adaptersimplement the hardware level of data communications connections throughwhich remote control devices communicate with UAVs directly or throughnetworks. Examples of communications adapters include modems for wireddial-up connections, Ethernet (IEEE 802.3) adapters for wired LANconnections, 802.11b adapters for wireless LAN connections, andBluetooth adapters for wireless microLAN connections.

The example remote control device (161) of FIG. 3 includes one or moreinput/output interface adapters (180). Input/output interface adaptersin computers implement user-oriented input/output through, for example,software drivers and computer hardware for controlling output to displaydevices (184) such as computer display screens, as well as user inputfrom user input devices (182) such as keypads, joysticks, keyboards, andtouch screens.

FIG. 4 sets forth a flow chart illustrating an exemplary method fornavigating a UAV that includes receiving (402) in a remote controldevice a user's selection of a GUI map pixel (412) that represents awaypoint for UAV navigation. The pixel has a location on the GUI. Such aGUI map display has many pixels, each of which represents at least oneposition on the surface of the Earth. A user selection of a pixel isnormal GUI operations to take a pixel location, row and column, from aGUI input/output adapter driven by a user input device such as ajoystick or a mouse. The control device can be a traditional ‘groundcontrol station,’ an airborne PDA or laptop, a workstation in Earthorbit, or any other control device capable of accepting user selectionsof pixels from a GUI map.

The method of FIG. 4 includes mapping (404) the pixel's location on theGUI to Earth coordinates of the waypoint (414). As discussed in moredetail below with reference to FIG. 5, mapping (404) the pixel'slocation on the GUI to Earth coordinates of the waypoint (414) typicallyincludes mapping pixel boundaries of the GUI map to corresponding Earthcoordinates and identifying a range of latitude and a range of longituderepresented by each pixel. Mapping (404) the pixel's location on the GUIto Earth coordinates of the waypoint (414) also typically includeslocating a region on the surface of the Earth in dependence upon theboundaries, the ranges, and the location of the pixel on the GUI map.

The method of FIG. 4 also includes transmitting (406) the coordinates ofthe waypoint to the UAV (100). Transmitting (406) the coordinates of thewaypoint to the UAV (100) may be carried out by use of any datacommunications protocol, including, for example, transmitting thecoordinates as form data, URI encoded data, in an HTTP message, a WAPmessage, an HDML message, or any other data communications protocolmessage as will occur to those of skill in the art.

The method of FIG. 4 also includes reading (408) a starting positionfrom a GPS receiver on the UAV (100) and piloting (410) the UAV, undercontrol of a navigation computer on the UAV, from the starting positionto the waypoint in accordance with a navigation algorithm (416). Methodsof piloting a UAV according to a navigation algorithm are discussed indetail below in this specification.

While piloting the UAV from the starting position to the waypoint, themethod of FIG. 4 also includes reading (418) from the GPS receiver asequence of GPS data representing a flight path of the UAV and depicting(420) the flight of the UAV with 3D computer graphics, including acomputer graphic display of a satellite image of the Earth, independence upon the GPS data. In the method of FIG. 4, depicting (420)the flight of the UAV includes determining (444) a display attitude ofthe UAV in dependence upon the sequence of GPS data. Display attitude isnot based upon actual attitude data such as would be had from gyrosensors, for example. In this disclosure, ‘display attitude’ refers todata describing orientation of a display image depicting a flight. Thedisplay attitude describes flight orientation in terms of roll, pitch,and yaw values derived from GPS data, not from measures of actual roll,pitch, and yaw.

In the method of FIG. 4, determining (444) a display attitude of the UAVin dependence upon the sequence of GPS data typically also includesdetecting changes in the UAV's course from the sequence of GPS data anddetermining a display roll angle in dependence upon the detected coursechanges. In some embodiments, a sequence of GPS locations is used tocalculate a rate of change of course, a value measured in degrees persecond. In such embodiments, display roll angle often is then determinedlinearly according to the rate of course change, so that a displayedangle of the wings on a UAV icon on a GUI display is proportional to therate of course change. The faster the course change, the steeper thedisplay roll angle.

It is useful to note, however, that there is no required relationshipbetween course change rate and display attitude. Embodiments of UAVnavigation systems according to embodiments of the present invention mayutilize no data whatsoever describing or representing the actualphysical flight attitude of a UAV. The determinations of ‘displayattitude’ are determination of values for data structures affecting aGUI display on a computer, not depictions of actual UAV attitude. To theextent that display attitudes are determined in calculated linearrelations to actual position changes or course change rates, suchdisplay attitudes may result in displays that model fairly closely theactual flight attitude of a UAV. This is not a limitation of theinvention, however. In fact, in some embodiments there is no attempt atall to determine display attitudes that closely model actual flightattitudes. Some embodiments consider it sufficient, for example, upondetecting a clockwise turn, always to simply assign a display roll angleof thirty degrees without more. Such embodiments do give a visualindication of roll, thereby indicating a turn, but they do not attemptto indicate an actual rate of change by varying the roll angle.

In the method of FIG. 4, determining (444) a display attitude of the UAVin dependence upon the sequence of GPS data may also include detectingchanges in the UAV's course from the sequence of GPS data anddetermining a display yaw angle in dependence upon the detected coursechanges. In the method of FIG. 4, determining (444) a display attitudeof the UAV in dependence upon the sequence of GPS data may also includedetecting changes in the UAV's altitude from the sequence of GPS dataand determining a display pitch angle in dependence upon the detectedaltitude changes.

FIG. 4A sets forth a flow chart illustrating an exemplary method ofdepicting the flight of the UAV. In the method of FIG. 4A, depicting theflight of the UAV includes determining (422), on the UAV, a displayattitude of the UAV in dependence upon the sequence of GPS data (430).In the method of FIG. 4A, depicting the flight of the UAV includescalculating (424), on the UAV, from the sequence of GPS data, the UAV'scourse. In the method of FIG. 4A, depicting the flight of the UAVincludes creating (426), on the UAV, images for display in dependenceupon the display attitude, the course, and a satellite image stored onthe UAV and downloading (428) the images for display from the UAV to theremote control device.

FIG. 4B sets forth a flow chart illustrating another exemplary method ofdepicting the flight of the UAV. In the method of FIG. 4B, depicting theflight of the UAV includes downloading (434) the GPS sequence (430) fromthe UAV to the remote control device and determining (436), in theremote control device, a display attitude of the UAV in dependence uponthe sequence of GPS data. In the method of FIG. 4B, depicting the flightof the UAV includes calculating (438), in the remote control device,from the sequence of GPS data, the UAV's course. In the method of FIG.4B, depicting the flight of the UAV includes creating (440), in theremote control device, images for display in dependence upon the displayattitude, the course, and a satellite image (442) stored on the remotecontrol device.

Whether the images for display are created on the UAV or on the remotecontrol device, UAV navigation systems according to embodiments of thepresent invention typically create images for display by use of 3Dgraphics rendering engines. One example of such an engine is DarkBasic™,from Enteractive Software, Inc., of Hartford, Conn. This example isdiscussed in terms of DarkBasic, but the use of DarkBasic is not alimitation of the present invention. Many other 3D graphics engines maybe used, including APIs for OpenGL, DirectX, Direct3D, and others aswill occur to those of skill in the art.

DarkBasic provides its API as an extended version of the Basicprogramming language for orienting a view of a JPEG map of the Earth'ssurface in accordance with data describing the location of a UAV overthe Earth and the UAV's attitude in terms of roll, pitch, yaw, andcourse. Satellite images of the Earth's surface in the form of JPEG mapssuitable for use in DarkBasic rendering engines are available, forexample, from Satellite Imaging Corporation of Houston, Tex. TheDarkBasic API commands “GET IMAGE” and “LOAD IMAGE” import JPEG imagesinto a DarkBasic rendering engine.

DarkBasic “CAMERA” commands are used to orient a view of a JPEG map. TheDarkBasic command “POSITION CAMERA” may be used to set an initial viewposition to a starting point and to move the view position to newlocations in dependence upon a sequence GPS data. The DarkBasic command“POINT CAMERA” may be used to orient the view to a UAV's course. Whendisplay attitudes are determined according to methods of the currentinvention, the DarkBasic commands “TURN CAMERA LEFT” and “TURN CAMERARIGHT” may be used to orient the view according to display yaw angle;the DarkBasic commands “PITCH CAMERA UP” and “PITCH CAMERA DOWN” may beused to orient the view according to display pitch angle; and theDarkBasic commands “ROLL CAMERA LEFT” and “ROLL CAMERA RIGHT” may beused to orient the view according to display roll angle.

Macros

Although the flow chart of FIG. 4 illustrates navigating a UAV to asingle waypoint, as a practical matter, embodiments of the presentinvention support navigating a UAV along a route having many waypoints,including a final waypoint and one or more intermediate waypoints. Thatis, methods of the kind illustrated in FIG. 4 may also include receivinguser selections of a multiplicity of GUI map pixels representingwaypoints, where each pixel has a location on the GUI and mapping eachpixel location to Earth coordinates of a waypoint.

Such methods of navigating a UAV can also include assigning one or moreUAV instructions to each waypoint and transmitting the coordinates ofthe waypoints and the UAV instructions to the UAV. A UAV instructiontypically includes one or more instructions for a UAV to perform a taskin connection with a waypoint. Exemplary tasks include turning on or offa camera installed on the UAV, turning on or off a light installed onthe UAV, orbiting a waypoint, or any other task that will occur to thoseof skill in the art.

Such exemplary methods of navigating a UAV also include storing thecoordinates of the waypoints and the UAV instructions in computer memoryon the UAV, piloting the UAV to each waypoint in accordance with one ormore navigation algorithms, and operating the UAV at each waypoint inaccordance with the UAV instructions for each waypoint. UAV instructionsto perform tasks in connection with a waypoint may be encoded in, forexample, XML (the extensible Markup Language) as shown in the followingexemplary XML segment:

<UAV-Instructions>

-   -   <macro>        -   <waypoint> 33° 44′ 10″ N 30° 15′ 50″ W </waypoint>        -   <instruction> orbit </instruction>        -   <instruction> videoCameraON </instruction>        -   <instruction> wait30minutes </instruction>        -   <instruction> videoCameraOFF </instruction>        -   <instruction> nextWaypoint </instruction>    -   </macro>    -   <macro> </macro>    -   <macro> </macro>    -   <macro> </macro>

<UAV-instructions>

This XML example has a root element named ‘UAV-instructions.’ Theexample contains several subelements named ‘macro.’ One ‘macro’subelement contains a waypoint location representing an instruction tofly to 33° 44′ 10″ N 30° 15′ 50″ W. That macro subelement also containsseveral instructions for tasks to be performed when the UAV arrives atthe waypoint coordinates, including orbiting around the waypointcoordinates, turning on an on-board video camera, continuing to orbitfor thirty minutes with the camera on, turning off the video camera, andcontinuing to a next waypoint. Only one macro set of UAV instructions isshown in this example, but that is not a limitation of the invention. Infact, such sets of UAV instructions may be of any useful size as willoccur to those of skill in the art.

Pixel Mapping

For further explanation of the process of mapping pixels' locations toEarth coordinates, FIG. 5 sets forth a block diagram that includes a GUI(502) displaying a map (not shown) and a corresponding area of thesurface of the Earth (504). The GUI map has pixel boundaries identifiedas Row₁, Col₁; Row₁, Col₁₀₀; Row₁₀₀ , Col₁₀₀ ; and Row₁₀₀, Col₁. In thisexample, the GUI map is assumed to comprise 100 rows of pixels and 100columns of pixels. This example of 100 rows and columns is presented forconvenience of explanation; it is not a limitation of the invention. GUImaps according to embodiments of the present invention may include anynumber of pixels as will occur to those of skill in the art.

The illustrated area of the surface of the Earth has correspondingboundary points identified as Lat₁, Lon₁; Lat₁, Lon₂; Lat₂, Lon₂; andLat₂, Lon₁. This example assumes that the distance along one side ofsurface area (504) is 100 nautical miles, so that the distance expressedin terms of latitude or longitude between boundary points of surfacearea (504) is 100 minutes or 1° 40′.

In typical embodiments, mapping a pixel's location on the GUI to Earthcoordinates of a waypoint includes mapping pixel boundaries of the GUImap to Earth coordinates. In this example, the GUI map boundary at Row₁,Col₁ maps to the surface boundary point at Lat₁, Lon₁; the GUI mapboundary at Row₁, Col₂ maps to the surface boundary point at Lat₁, Lon₂;the GUI map boundary at Row₂, Col₂ maps to the surface boundary point atLat₂, Lon₂; the GUI map boundary at Row₂, Col₁ maps to the surfaceboundary point at Lat₂, Lon₁.

Mapping a pixel's location on the GUI to Earth coordinates of a waypointtypically also includes identifying a range of latitude and a range oflongitude represented by each pixel. The range of latitude representedby each pixel may be described as (Lat₂−Lat₁)/N_(rows), where(Lat₂−Lat₁) is the length in degrees of the vertical side of thecorresponding surface (504), and N_(rows) is the number of rows ofpixels. In this example, (Lat₂−Lat₁) is 1° 40′ or 100 nautical miles,and N_(rows) is 100 rows of pixels. The range of latitude represented byeach pixel in this example therefore is one minute of arc or onenautical mile.

Similarly, the range of longitude represented by each pixel may bedescribed as (Lon₂−Lon₁)/N_(cols), where (Lon₂−Lon₁) is the length indegrees of the horizontal side of the corresponding surface (504), andN_(cols) is the number of columns of pixels. In this example,(Lon₂−Lon₁) is 1° 40′ or 100 nautical miles, and N_(cols) is 100 columnsof pixels. The range of longitude represented by each pixel in thisexample therefore is one minute of arc or one nautical mile.

Mapping a pixel's location on the GUI to Earth coordinates of a waypointtypically also includes locating a region on the surface of the Earth independence upon the boundaries, the ranges, and the location of thepixel on the GUI map. The region is the portion of the surfacecorresponding the pixel itself. That region is located generally bymultiplying in both dimension, latitude and longitude, the range oflatitude and longitude by column or row numbers of the pixel location onthe GUI map. That is, a latitude for the surface region of interest isgiven by Expression 1.Lat₁+P_(row)((Lat₂−Lat₁)/N_(rows))  (Exp. 1)

In Expression 1:

-   -   Lat₁ is the latitude of an origin point for the surface area        (504) corresponding generally to the GUI map,    -   P_(row) is the row number of the pixel location on the GUI map,        and    -   ((Lat₂−Lat₁)/N_(rows)) is the range of latitude represented by        the pixel.

Similarly, a longitude for the surface region of interest is given byExpression 2.Lon₁+P_(col)((Lon₂−Lon₁)/N_(cols))  (Exp. 2)

In Expression 2:

-   -   Lon₁ is the longitude of an origin point for the surface area        (504) corresponding generally to the GUI map,    -   P_(col) is the column number of the pixel location on the GUI        map, and    -   ((Lon₂−Lon₁)/N_(cols)) is the range of longitude represented by        the pixel.

Referring to FIG. 5 for further explanation, Expressions 1 and 2 takentogether identify a region (508) of surface area (504) that correspondsto the location of pixel (412) mapping the pixel location to the bottomleft corner (506) of the region (508). Advantageously, however, manyembodiments of the present invention further map the pixel to the centerof the region by adding one half of the length of the region's sides tothe location of the bottom left corner (506).

More particularly, locating a region on the surface of the Earth independence upon the boundaries, the ranges, and the location of thepixel on the GUI map, as illustrated by Expression 3, may includemultiplying the range of longitude represented by each pixel by a columnnumber of the selected pixel, yielding a first multiplicand; andmultiplying the range of longitude represented by each pixel by 0.5,yielding a second multiplicand; adding the first and secondmultiplicands to an origin longitude of the GUI map.Lon₁+P_(col)((Lon₂−Lon₁)/N_(cols))+0.5((Lon₂−Lon₁)/N_(cols))  (Exp. 3)

In Expression 3, the range of longitude represented by each pixel isgiven by ((Lon₂−Lon₁)/N_(cols)), and the first multiplicand isP_(col)((Lon₂−Lon₁)/N_(cols)). The second multiplicand is given by0.5((Lon₂−Lon₁)/N_(cols)).

Similarly, locating a region on the surface of the Earth in dependenceupon the boundaries, the ranges, and the location of the pixel on theGUI map, as illustrated by Expression 4, typically also includesmultiplying the range of latitude represented by each pixel by a rownumber of the selected pixel, yielding a third multiplicand; multiplyingthe range of latitude represented by each pixel by 0.5, yielding afourth multiplicand; and adding the third and fourth multiplicands to anorigin latitude of the GUI map.Lat₁+P_(row)((Lat₂−Lat₁)/N_(rows))+0.5((Lat₂−Lat₁)/N_(rows))  (Exp. 4)

In Expression 4, the range of latitude represented by each pixel isgiven by ((Lat₂−Lat₁)/N_(rows)), and the third multiplicand isP_(row)((Lat₂−Lat₁)/N_(rows)). The fourth multiplicand is given by0.5((Lat₂−Lat₁)/N_(rows)). Expressions 3 and 4 taken together map thelocation of pixel (412) to the center (510) of the located region (508).

Navigation on a Heading to a Waypoint

An exemplary method of navigating in accordance with a navigationalgorithm is explained with reference to FIGS. 6 and 7. FIG. 6 setsforth a flow chart illustrating an exemplary method of piloting inaccordance with a navigation algorithm, and FIG. 7 sets forth a linedrawing illustrating a flight path produced by application of the methodof FIG. 6. The method of FIG. 6 includes periodically repeating (610)the steps of:

-   -   reading (602) from the GPS receiver a current position of the        UAV;    -   calculating (604) a heading from the current position to the        waypoint;    -   turning (606) the UAV to the heading; and    -   flying (608) the UAV on the heading.

In this method, if Lon₁, Lat₁, is taken as the current position, andLon₂, Lat₂ is taken as the waypoint position, then the heading may becalculated generally as the inverse tangent of((Lat₂−Lat₁)/(Lon₂−Lon₁)).

FIG. 7 shows the effect of the application of the method of FIG. 6. Inthe example of FIG. 7, a UAV is flying in a cross wind having cross windvector (708). Curved flight path (716) results from periodiccalculations according to the method of FIG. 6 of a new heading straightfrom a current location to the waypoint. FIG. 7 shows periodicrepetitions of the method of FIG. 6 at plot points (710, 712, 714). Forclarity of explanation, only three periodic repetitions are shown,although that is not a limitation of the invention. In fact, any numberof periodic repetitions may be used as will occur to those of skill inthe art.

Navigation with Headings Set to a Cross Track Direction

A further exemplary method of navigating in accordance with a navigationalgorithm is explained with reference to FIGS. 8 and 9. FIG. 8 setsforth a flow chart illustrating an exemplary method of piloting inaccordance with a navigation algorithm, and FIG. 9 sets forth a linedrawing illustrating a flight path produced by application of the methodof FIG. 8.

The method of FIG. 8 includes identifying (802) a cross track betweenthe starting point and the waypoint. A cross track is a fixed coursefrom a starting point directly to a waypoint. If Lon₁, Lat₁, is taken asthe position of a starting point, and Lon₂, Lat₂ is taken as thewaypoint position, then a cross track is identified by Lon₁, Lat₁ andLon₂, Lat₂. A cross track has a direction, a ‘cross track direction,’that is the direction straight from a starting point to a waypoint, andit is often useful to characterize a cross track by its cross trackdirection. The cross track direction for a cross track identified bystarting point Lon₁, Lat₁ and waypoint position Lon₂, Lat₂ may becalculated generally as the inverse tangent of((Lat₂−Lat₁)/(Lon₂−Lon₁)).

The method of FIG. 8 includes periodically repeating (810) the steps of:reading (804) from the GPS receiver a current position of the UAV;calculating (806) a shortest distance between the current position andthe cross track; and if the shortest distance between the currentposition and the cross track is greater than a threshold distance,piloting (812) the UAV toward the cross track, and, upon arriving at thecross track, piloting (814) the UAV in a cross track direction towardthe waypoint. FIG. 9 illustrates calculating a shortest distance betweenthe current position and a cross track. In the example of FIG. 9,calculating a shortest distance between the current position and a crosstrack includes calculating the distance from a current position (912) tothe waypoint (704). In the example of FIG. 9, the distance from thecurrent position (912) to the waypoint (704) is represented as thelength of line (914). For current position Lon₁, Lat₁ and waypointposition Lon₂, Lat₂, the distance from a current position (912) to thewaypoint (704) is given by the square root of (Lat₂−Lat₁)²+(Lon₂−Lon₁)².

In this example, calculating a shortest distance between the currentposition and a cross track also includes calculating the angle (910)between a direction from the current position to the waypoint and across track direction. In the example of FIG. 9, the direction from thecurrent position (912) to the waypoint (704) is represented as thedirection of line (914). In the example of FIG. 9, the cross trackdirection is the direction of cross track (706). The angle between adirection from the current position to the waypoint and a cross trackdirection is the difference between those directions.

In the current example, calculating a shortest distance between thecurrent position and a cross track also includes calculating the tangentof the angle between a direction from the current position to thewaypoint and a cross track direction and multiplying the tangent of theangle by the distance from the current position to the waypoint.

FIG. 9 also shows the effect of the application of the method of FIG. 8.In the example of FIG. 9, a UAV is flying in a cross wind having crosswind vector (708). Curved flight path (904) results from periodiccalculations according to the method of FIG. 8 of a shortest distancebetween a current position and the cross track (706), flying the UAVback to the cross track and then in the direction of the cross trackwhenever the distance from the cross track exceeds a predeterminedthreshold distance.

Headings Set to Cross Track Direction with Angular Thresholds

A further exemplary method of navigating in accordance with a navigationalgorithm is explained with reference to FIGS. 10 and 11. FIG. 10 setsforth a flow chart illustrating an exemplary method of piloting inaccordance with a navigation algorithm, and FIG. 11 sets forth a linedrawing illustrating a flight path produced by application of the methodof FIG. 10.

In the method of FIG. 10, piloting in accordance with a navigationalgorithm includes identifying (1002) a cross track having a cross trackdirection between the starting point and the waypoint. As describedabove, a cross track is identified by a position of a starting point anda waypoint position. For a starting point position of Lon₁, Lat₁ and awaypoint position of Lon₂, Lat₂, a cross track is identified by Lon₁,Lat₁ and Lon₂, Lat₂. In addition, it is often also useful tocharacterize a cross track by its cross track direction. The cross trackdirection for a cross track identified by starting point Lon₁, Lat₁ andwaypoint position Lon₂, Lat₂ may be calculated generally as the inversetangent of ((Lat₂−Lat₁)/(Lon₂−Lon₁)).

In the method of FIG. 10, piloting in accordance with a navigationalgorithm also includes repeatedly (1010) carrying out the steps ofreading (1004) from the GPS receiver a current position of the UAV;calculating (1006) an angle between the direction from the currentposition to the waypoint and a cross track direction; and, if the angleis greater than a threshold angle, piloting (1012) the UAV toward thecross track, and, upon arriving at the cross track, piloting (1014) theUAV in the cross track direction. Piloting toward the cross track iscarried out by turning to a heading no more than ninety degrees from thecross track direction, turning to the left if the current position isright of the cross track and to the right if the current position isleft of the cross track. Piloting in the cross track direction meansturning the UAV to the cross track direction and then flying straightand level on the cross track direction. That is, in piloting in thecross track direction, the cross track direction is set as the compassheading for the UAV.

FIG. 11 shows the effect of the application of the method of FIG. 10. Inthe example of FIG. 11, a UAV is flying in a cross wind having crosswind vector (708). Curved flight path (1104) results from periodicallyflying the UAV, according to the method of FIG. 10, back to the crosstrack and then in the direction of the cross track whenever an anglebetween the direction from the current position to the waypoint and across track direction exceeds a predetermined threshold angle.

In many embodiments of the method of FIG. 10, the threshold angle is avariable whose value varies in dependence upon a distance between theUAV and the waypoint. In typical embodiments that vary the thresholdangle, the threshold angle is increased as the UAV flies closer to thewaypoint. It is useful to increase the threshold angle as the UAV fliescloser to the waypoint to reduce the risk of excessive ‘hunting’ on thepart of the UAV. That is, because the heading is the cross trackdirection, straight to the WP rather than cross-wind, if the angleremains the same, the distance that the UAV needs to be blown off courseto trigger a return to the cross track gets smaller and smaller untilthe UAV is flying to the cross track, turning to the cross trackdirection, getting blown immediately across the threshold, flying backthe cross track, turning to the cross track direction, getting blownimmediately across the threshold, and so on, and so on, in rapidrepetition. Increasing the threshold angle as the UAV flies closer tothe waypoint increases the lateral distance available for wind errorbefore triggering a return to the cross track, thereby reducing thisrisk of excessive hunting.

Navigation on a Course to a Waypoint

A further exemplary method of navigating in accordance with a navigationalgorithm is explained with reference to FIGS. 12, 12A, and 13. FIG. 12sets forth a flow chart illustrating an exemplary method of piloting inaccordance with a navigation algorithm. FIG. 12A sets forth a linedrawing illustrating a method of calculating a heading with a cross windto achieve a particular ground course. And FIG. 13 sets forth a linedrawing illustrating a flight path produced by application of the methodof FIG. 12.

In the method of FIG. 12, piloting in accordance with a navigationalgorithm comprises periodically repeating (1212) the steps of reading(1202) from the GPS receiver a current position of the UAV; calculating(1204) a direction to the waypoint from the current position;calculating (1206) a heading in dependence upon wind speed, winddirection, air speed, and the direction to the waypoint; turning (1208)the UAV to the heading; and flying (1210) the UAV on the heading.

FIG. 12A illustrates calculating (1206) a heading in dependence uponwind speed, wind direction, air speed, and the direction to thewaypoint. FIG. 12A sets forth a line drawing illustrating relationsamong several pertinent vectors, a wind velocity (1222), a resultantvelocity (1224), and a UAV's air velocity (1226). A velocity vectorincludes a speed and a direction. These vectors taken together representwind speed, wind direction, air speed, and the direction to thewaypoint. In the example of FIG. 12A, the angle B is a so-called windcorrection angle, an angle which subtracted from (or added to, dependingon wind direction) a direction to a waypoint yields a heading, a compassheading for a UAV to fly so that is resultant ground course is on across track. A UAV traveling at an air speed of ‘a’ on heading (D–B) inthe presence of a wind speed ‘b’ with wind direction E will haveresultant ground speed ‘c’ in direction D.

In FIG. 12A, angle A represents the difference between the winddirection E and the direction to the waypoint D. In FIG. 12A, the windvelocity vector (1222) is presented twice, once to show the winddirection as angle E and again to illustrate angle A as the differencebetween angles E and D. Drawing wind velocity (1222) to form angle Awith the resultant velocity (1224) also helps explain how to calculatewind correction angle B using the law of sines. Knowing two sides of atriangle and the angle opposite one of them, the angle opposite theother may be calculated, in this example, by B=sin⁻¹(b(sin A)/a). Thetwo known sides are airspeed ‘a’ and wind speed ‘b.’ The known angle isA, the angle opposite side ‘a,’ representing the difference between winddirection E and direction to the waypoint D. Calculating a heading,angle F on FIG. 12A, is then carried out by subtracting the windcorrection angle B from the direction to the waypoint D.

FIG. 13 shows the effect of the application of the method of FIG. 12. Inthe example of FIG. 13, a UAV is flying in a cross wind having crosswind vector (708). Curved flight path (1316) results from periodiccalculations according to the method of FIG. 12 of a new headingstraight whose resultant with a wind vector is a course straight from acurrent location to the waypoint. FIG. 13 shows periodic repetitions ofthe method of FIG. 12 at plot points (1310, 1312, 1314). For clarity ofexplanation, only three periodic repetitions are shown, although that isnot a limitation of the invention. In fact, any number of periodicrepetitions may be used as will occur to those of skill in the art.

Navigation on a Course Set to a Cross Track Direction

A further exemplary method of navigating in accordance with a navigationalgorithm is explained with reference to FIGS. 14 and 15. FIG. 14 setsforth a flow chart illustrating an exemplary method of piloting inaccordance with a navigation algorithm, and FIG. 15 sets forth a linedrawing illustrating a flight path produced by application of the methodof FIG. 14.

The method of FIG. 14 includes identifying (1402) a cross track andcalculating (1404) a cross track direction from the starting position tothe waypoint. In the method of FIG. 14, piloting in accordance with anavigation algorithm is carried out by periodically repeating the stepsof reading (1406) from the GPS receiver a current position of the UAV;calculating (1408) a shortest distance between the cross track and thecurrent position; and, if the shortest distance between the cross trackand the current position is greater than a threshold distance, piloting(1412) the UAV to the cross track. Upon arriving at the cross track, themethod includes: reading (1414) from the GPS receiver a new currentposition of the UAV; calculating (1416), in dependence upon wind speed,wind direction, air speed, and the cross track direction, a new heading;turning (1418) the UAV to the new heading; and flying (1420) the UAV onthe new heading.

FIG. 15 shows the effect of the application of the method of FIG. 14. Inthe example of FIG. 15, a UAV is flying in a cross wind having crosswind vector (708). Curved flight path (1304) results from periodiccalculations according to the method of FIG. 14 of a shortest distancebetween a current position and the cross track (706), flying the UAVback to the cross track, and, upon arriving at the cross track,calculating a new heading and flying the UAV on the new heading.

It will be understood from the foregoing description that modificationsand changes may be made in various embodiments of the present inventionwithout departing from its true spirit. The descriptions in thisspecification are for purposes of illustration only and are not to beconstrued in a limiting sense. The scope of the present invention islimited only by the language of the following claims.

1. A method for navigating a UAV, the method comprising: receiving in aremote control device a user's selection of a GUI map pixel thatrepresents a waypoint for UAV navigation, the pixel having a location onthe GUI; mapping the pixel's location on the GUI to Earth coordinates ofthe waypoint; transmitting the coordinates of the waypoint to the UAV;reading a starting position from a GPS receiver on the UAV; piloting theUAV, under control of a navigation computer on the UAV, from thestarting position to the waypoint in accordance with a navigationalgorithm; and while piloting the UAV from the starting position to thewaypoint: reading from the GPS receiver a sequence of GPS datarepresenting a flight path of the UAV; and depicting the flight of theUAV with 3D computer graphics, including a computer graphic display of asatellite image of the Earth, in dependence upon the GPS data.
 2. Themethod of claim 1 wherein depicting the flight of the UAV furthercomprises: determining, on the UAV, a display attitude of the UAV independence upon the sequence of GPS data; calculating, on the UAV, fromthe sequence of GPS data, the UAV's course; creating, on the UAV, imagesfor display in dependence upon the display attitude, the course, and asatellite image stored on the UAV; and downloading the images fordisplay from the UAV to the remote control device.
 3. The method ofclaim 1 wherein depicting the flight of the UAV further comprises:downloading the GPS sequence from the UAV to the remote control device;determining, in the remote control device, a display attitude of the UAVin dependence upon the sequence of GPS data; calculating, in the remotecontrol device, from the sequence of GPS data, the UAV's course; andcreating, in the remote control device, images for display in dependenceupon the display attitude, the course, and a satellite image stored onthe remote control device.
 4. The method of claim 1 wherein depictingthe flight of the UAV further comprises determining a display attitudeof the UAV in dependence upon the sequence of GPS data, including:detecting changes in the UAV's course from the sequence of GPS data;determining a display roll angle in dependence upon the detected coursechanges.
 5. The method of claim 1 wherein depicting the flight of theUAV further comprises determining a display attitude of the UAV independence upon the sequence of GPS data, including: detecting changesin the UAV's course from the sequence of GPS data; determining a displayyaw angle in dependence upon the detected course changes.
 6. The methodof claim 1 wherein depicting the flight of the UAV further comprisesdetermining a display attitude of the UAV in dependence upon thesequence of GPS data, including: detecting changes in the UAV's altitudefrom the sequence of GPS data; determining a display pitch angle independence upon the detected altitude changes.
 7. The method of claim 1further comprising: receiving user selections of a multiplicity of GUImap pixels representing waypoints, each pixel having a location on theGUI mapping each pixel location to Earth coordinates of a waypoint;assigning one or more UAV instructions to each waypoint; transmittingthe coordinates of the waypoints and the UAV instructions to the UAV;storing the coordinates of the waypoints and the UAV instructions incomputer memory on the UAV; piloting the UAV to each waypoint inaccordance with one or more navigation algorithms; and operating the UAVat each waypoint in accordance with the UAV instructions for eachwaypoint.
 8. The method of claim 1 wherein mapping the pixel's locationon the GUI to Earth coordinates of the waypoint further comprises:mapping pixel boundaries of the GUI map to Earth coordinates;identifying a range of latitude and a range of longitude represented byeach pixel; and locating a region on the surface of the Earth independence upon the boundaries, the ranges, and the location of thepixel on the GUI map.
 9. The method of claim 8 wherein locating a regionon the surface of the Earth in dependence upon the boundaries, theranges, and the location of the pixel on the GUI map further comprises:multiplying the range of longitude represented by each pixel by a columnnumber of the selected pixel, yielding a first multiplicand; multiplyingthe range of longitude represented by each pixel by 0.5, yielding asecond multiplicand; adding the first and second multiplicands to anorigin longitude of the GUI map; multiplying the range of latituderepresented by each pixel by a row number of the selected pixel,yielding a third multiplicand; multiplying the range of latituderepresented by each pixel by 0.5, yielding a fourth multiplicand; andadding the third and fourth multiplicands to an origin latitude of theGUI map.
 10. A system for navigating a UAV, the system comprising: meansfor receiving in a remote control device a user's selection of a GUI mappixel that represents a waypoint for UAV navigation, the pixel having alocation on the GUI; means for mapping the pixel's location on the GUIto Earth coordinates of the waypoint; means for transmitting thecoordinates of the waypoint to the UAV; means for reading a startingposition from a GPS receiver on the UAV; means for piloting the UAV,under control of a navigation computer on the UAV, from the startingposition to the waypoint in accordance with a navigation algorithm; andwhile piloting the UAV from the starting position to the waypoint: meansfor reading from the GPS receiver a sequence of GPS data representing aflight path of the UAV; and means for depicting the flight of the UAVwith 3D computer graphics, including a computer graphic display of asatellite image of the Earth, in dependence upon the GPS data.
 11. Thesystem of claim 10 wherein means for depicting the flight of the UAVfurther comprises: means for determining, on the UAV, a display attitudeof the UAV in dependence upon the sequence of GPS data; means forcalculating, on the UAV, from the sequence of GPS data, the UAV'scourse; means for creating, on the UAV, images for display in dependenceupon the display attitude, the course, and a satellite image stored onthe UAV; and means for downloading the images for display from the UAVto the remote control device.
 12. The system of claim 10 wherein meansfor depicting the flight of the UAV further comprises: means fordownloading the GPS sequence from the UAV to the remote control device;means for determining, in the remote control device, a display attitudeof the UAV in dependence upon the sequence of GPS data; means forcalculating, in the remote control device, from the sequence of GPSdata, the UAV's course; and means for creating, in the remote controldevice, images for display in dependence upon the display attitude, thecourse, and a satellite image stored on the remote control device. 13.The system of claim 10 wherein means for depicting the flight of the UAVfurther comprises means for determining a display attitude of the UAV independence upon the sequence of GPS data, including: means for detectingchanges in the UAV's course from the sequence of GPS data; means fordetermining a display roll angle in dependence upon the detected coursechanges.
 14. The system of claim 10 wherein means for depicting theflight of the UAV further comprises means for determining a displayattitude of the UAV in dependence upon the sequence of GPS data,including: means for detecting changes in the UAV's course from thesequence of GPS data; means for determining a display yaw angle independence upon the detected course changes.
 15. The system of claim 10wherein means for depicting the flight of the UAV further comprisesmeans for determining a display attitude of the UAV in dependence uponthe sequence of GPS data, including: means for detecting changes in theUAV's altitude from the sequence of GPS data; means for determining adisplay pitch angle in dependence upon the detected altitude changes.16. The system of claim 10 further comprising: means for receiving userselections of a multiplicity of GUI map pixels representing waypoints,each pixel having a location on the GUI means for mapping each pixellocation to Earth coordinates of a waypoint; means for assigning one ormore UAV instructions to each waypoint; means for transmitting thecoordinates of the waypoints and the UAV instructions to the UAV; meansfor storing the coordinates of the waypoints and the UAV instructions incomputer memory on the UAV; means for piloting the UAV to each waypointin accordance with one or more navigation algorithms; and means foroperating the UAV at each waypoint in accordance with the UAVinstructions for each waypoint.
 17. The system of claim 10 wherein meansfor mapping the pixel's location on the GUI to Earth coordinates of thewaypoint further comprises: means for mapping pixel boundaries of theGUI map to Earth coordinates; means for identifying a range of latitudeand a range of longitude represented by each pixel; and means forlocating a region on the surface of the Earth in dependence upon theboundaries, the ranges, and the location of the pixel on the GUI map.18. The system of claim 17 wherein means for locating a region on thesurface of the Earth in dependence upon the boundaries, the ranges, andthe location of the pixel on the GUI map further comprises: means formultiplying the range of longitude represented by each pixel by a columnnumber of the selected pixel, yielding a first multiplicand; means formultiplying the range of longitude represented by each pixel by 0.5,yielding a second multiplicand; means for adding the first and secondmultiplicands to an origin longitude of the GUI map; means formultiplying the range of latitude represented by each pixel by a rownumber of the selected pixel, yielding a third multiplicand; means formultiplying the range of latitude represented by each pixel by 0.5,yielding a fourth multiplicand; and means for adding the third andfourth multiplicands to an origin latitude of the GUI map.
 19. Acomputer program product for navigating a UAV, the computer programproduct comprising: a recording medium; means, recorded on the recordingmedium, for receiving in a remote control device a user's selection of aGUI map pixel that represents a waypoint for UAV navigation, the pixelhaving a location on the GUI; means, recorded on the recording medium,for mapping the pixel's location on the GUI to Earth coordinates of thewaypoint; means, recorded on the recording medium, for transmitting thecoordinates of the waypoint to the UAV; means, recorded on the recordingmedium, for reading a starting position from a GPS receiver on the UAV;means, recorded on the recording medium, for piloting the UAV, undercontrol of a navigation computer on the UAV, from the starting positionto the waypoint in accordance with a navigation algorithm; and whilepiloting the UAV from the starting position to the waypoint: means,recorded on the recording medium, for reading from the GPS receiver asequence of GPS data representing a flight path of the UAV; and means,recorded on the recording medium, for depicting the flight of the UAVwith 3D computer graphics, including a computer graphic display of asatellite image of the Earth, in dependence upon the GPS data.
 20. Thecomputer program product of claim 19 wherein means, recorded on therecording medium, for depicting the flight of the UAV further comprises:means, recorded on the recording medium, for determining, on the UAV, adisplay attitude of the UAV in dependence upon the sequence of GPS data;means, recorded on the recording medium, for calculating, on the UAV,from the sequence of GPS data, the UAV's course; means, recorded on therecording medium, for creating, on the UAV, images for display independence upon the display attitude, the course, and a satellite imagestored on the UAV; and means, recorded on the recording medium, fordownloading the images for display from the UAV to the remote controldevice.
 21. The computer program product of claim 19 wherein means,recorded on the recording medium, for depicting the flight of the UAVfurther comprises: means, recorded on the recording medium, fordownloading the GPS sequence from the UAV to the remote control device;means, recorded on the recording medium, for determining, in the remotecontrol device, a display attitude of the UAV in dependence upon thesequence of GPS data; means, recorded on the recording medium, forcalculating, in the remote control device, from the sequence of GPSdata, the UAV's course; and means, recorded on the recording medium, forcreating, in the remote control device, images for display in dependenceupon the display attitude, the course, and a satellite image stored onthe remote control device.
 22. The computer program product of claim 19wherein means, recorded on the recording medium, for depicting theflight of the UAV further comprises means, recorded on the recordingmedium, for determining a display attitude of the UAV in dependence uponthe sequence of GPS data, including: means, recorded on the recordingmedium, for detecting changes in the UAV's course from the sequence ofGPS data; means, recorded on the recording medium, for determining adisplay roll angle in dependence upon the detected course changes. 23.The computer program product of claim 19 wherein means, recorded on therecording medium, for depicting the flight of the UAV further comprisesmeans, recorded on the recording medium, for determining a displayattitude of the UAV in dependence upon the sequence of GPS data,including: means, recorded on the recording medium, for detectingchanges in the UAV's course from the sequence of GPS data; means,recorded on the recording medium, for determining a display yaw angle independence upon the detected course changes.
 24. The computer programproduct of claim 19 wherein means, recorded on the recording medium, fordepicting the flight of the UAV further comprises means, recorded on therecording medium, for determining a display attitude of the UAV independence upon the sequence of GPS data, including: means, recorded onthe recording medium, for detecting changes in the UAV's altitude fromthe sequence of GPS data; means, recorded on the recording medium, fordetermining a display pitch angle in dependence upon the detectedaltitude changes.
 25. The computer program product of claim 19 furthercomprising: means, recorded on the recording medium, for receiving userselections of a multiplicity of GUI map pixels representing waypoints,each pixel having a location on the GUI means, recorded on the recordingmedium, for mapping each pixel location to Earth coordinates of awaypoint; means, recorded on the recording medium, for assigning one ormore UAV instructions to each waypoint; means, recorded on the recordingmedium, for transmitting the coordinates of the waypoints and the UAVinstructions to the UAV; means, recorded on the recording medium, forstoring the coordinates of the waypoints and the UAV instructions incomputer memory on the UAV; means, recorded on the recording medium, forpiloting the UAV to each waypoint in accordance with one or morenavigation algorithms; and means, recorded on the recording medium, foroperating the UAV at each waypoint in accordance with the UAVinstructions for each waypoint.
 26. The computer program product ofclaim 19 wherein means, recorded on the recording medium, for mappingthe pixel's location on the GUI to Earth coordinates of the waypointfurther comprises: means, recorded on the recording medium, for mappingpixel boundaries of the GUI map to Earth coordinates; means, recorded onthe recording medium, for identifying a range of latitude and a range oflongitude represented by each pixel; and means, recorded on therecording medium, for locating a region on the surface of the Earth independence upon the boundaries, the ranges, and the location of thepixel on the GUI map.
 27. The computer program product of claim 26wherein means, recorded on the recording medium, for locating a regionon the surface of the Earth in dependence upon the boundaries, theranges, and the location of the pixel on the GUI map further comprises:means, recorded on the recording medium, for multiplying the range oflongitude represented by each pixel by a column number of the selectedpixel, yielding a first multiplicand; means, recorded on the recordingmedium, for multiplying the range of longitude represented by each pixelby 0.5, yielding a second multiplicand; means, recorded on the recordingmedium, for adding the first and second multiplicands to an originlongitude of the GUI map; means, recorded on the recording medium, formultiplying the range of latitude represented by each pixel by a rownumber of the selected pixel, yielding a third multiplicand; means,recorded on the recording medium, for multiplying the range of latituderepresented by each pixel by 0.5, yielding a fourth multiplicand; andmeans, recorded on the recording medium, for adding the third and fourthmultiplicands to an origin latitude of the GUI map.